Although disc-type coin sorters with resilient discs have been used for a number of years, problems are still encountered in applying this technology to certain types of coin sets. Sorting heads for coin mixtures which include two coin denominations of only slightly different diameters may encounter difficulty in discriminating between coins of the different denominations. Because all coins to be sorted are usually aligned with their outer edges at a common radial position defined by a gaging wall, and different denominations are discriminated by the distance of their inner edges from that gaging wall, coins of similar size must be precisely aligned with their outer edges against the common gaging wall in order to enter the appropriate exit channel. For example, a coin that moves just slightly beyond the common radial position may enter an exit channel intended for a smaller diameter coin. Rather than passing on to the appropriate exit channel, the larger denomination coin is issued from the exit channel intended for the smaller coin denomination. This is a coin missort.
The "target" for any given coin is the innermost end of the inboard wall of the exit channel provided for that denomination. It is the precise location of this target area of each channel, relative to the gaging wall, that determines whether or not coins of only the desired denomination enter each channel. Variations of only one or two thousandths of an inch between the gaging wall and the target area of the exit channel wall can result in missorts, especially with coin sets in which the diameters of different coin denominations differ from each other by only six thousandths of an inch.